The invention relates to arc interrupters in which the arc is rotated about an axis to assist in extinguishment of the arc.
There have been a number of proposals to rotate an arc to assist its extinguishment, one early example being disclosed in UK Pat. No. 478890. More recent examples, with arc interrupters which function in an insulating fluid, for example, sulphur hexafluoride (SF.sub.6) gas under pressure, are to be found in a paper by Fujiwara K., Ono S. I., entitled "Rotating Arc Driven by Magnetic Flux in SF.sub.6 Gas", in UK Pat. application Nos. 2038100A, 2082391A, 2178239A, 2188486A, 2188487A, and 2188488A, and in UK Pat. No. 2119573B. In most of these examples the arc interrupters have a fixed contact and an angularly movable contact, an annular arcing electrode and an arc-driving coil located about the electrode and electrically connected in series with the electrode. In the case of UK Patent Application No. 2082391, the movable contact is axially displaced away from the fixed contact for the break operation and carries an arcing contact that is axially displaceable with it. When the fixed and movable contacts break, the arcing contact establishes an arc between an inner conductor encircling an arc-driving coil mounted on the fixed contact and an outer conductor maintained in conductive contact with the movable contact. In all these examples, the arc, once fully established, extends between the electrode and one of the contacts or a surface electrically continuous therewith and is driven about the central axis of the electrode by the magnetic field generated by the coil.
These known forms of arc interrupter have certain limitations. In the case of GB No. 2082391A, the axial displacement arrangement results in a construction which is considerably larger than would otherwise be the case. Problems can arise with the other examples of arc interrupter as the rating of the interrupter is increased; the electrode can distort or collapse owing to the increased magnetic fields generated by the currents induced in the electrode as a result of the magnetic fields generated by the coil, the respective magnetic fields being in opposition to each other. Also, in arrangements such as that shown in UK Pat. Application No. 2119573A, the mounting and construction of the coil and electrode arrangement is relatively complex.
It is an object of the present invention to provide an arc interrupter in which the aforementioned problems are reduced or obviated.